The present invention relates to an apparatus for detecting and reporting or signalling the presence of liquid on a surface, and includes a detector unit that rests on the surface and an operations unit, with the detector unit and the operations unit being electrically interconnected.
Not only in the industrial arena, such as manufacturing plants, workshops, warehouses, offices, studios, and public facilities, but also in the private arena, such as in the household, enormous damage can result from discharging or leaking liquids, such as water, heating unit fluids, various hydrocarbons such as Diesel oil and gasoline, if the presence of these or any other liquids is not detected early enough. A number of attempts, some technically extremely complicated, have been undertaken to provide apparatus for systems that are in a position to detect and subsequently trigger an alarm concerning the presence of liquids that collect on an essentially flat base, for example on floors, as a result, for example, of a defect in a conveying line. Although it is still relatively easy to realize means for detecting a liquid such as water that, at least if it originates from a heating system, has a relatively good electrical conductivity, it has up
now been extremely difficult, and actually without success, to provide detection means that with the same sensitivity are in a position to detect water originating from a heating system, water originating from a drinking water supply, as well as water originating from an air conditioning unit. A common detection of water originating from the aforementioned different sources is so extremely difficult for the reason that the electrical conductivity of water originating from a heating circuit is good, while the conductivity of water originating from a drinking water supply system is weak and water originating from an air conditioning unit has absolutely no electrical conductivity because such water must, by design, be demineralized. Up to now, in order in conformity with the very different conductivities of the various types of water, in each case separate apparatus had to be provided to be able to resolve such a problem at all.
As indicated above, the problems are, however, not exhausted by the detection of the various "water" liquids; rather, other liquids such as Diesel oil, volatile solvents, resins, cleaning fluids liquids used for cooling purposes. etc., cause much greater problems with regard to their detection when they are discharged or collect on a surface, such as the floor of a workshop or a warehouse, because such liquids generally have absolutely no electrical conductivity, and conductive agents for detecting these liquids are completely impossible to use, in contrast to the situation with aqueous solutions and water. Attempts have been made to detect such liquids in a capacitative manner, and to utilize the physical property of the differing magnitude of the dielectric constants .SIGMA..sub.r, whereby, for example, oil has a dielectric constant of .SIGMA..sub.r =2 to 3, while water has a dielectric constant of .SIGMA..sub.r =81. Thus, if a liquid level is to be detected pursuant to the capacitative method, it is roughly estimated that water would already have to have a level of 2 mm to be detected, while oil, due to its very small dielectric constant relative to water, could not be detected until a level of about 10 mm has been reached. Thus, the approach of determining the liquid level in a capacitative manner cannot be carried out without extreme capital outlay and measuring effort for liquids having varying dielectric constants.
Finally, a further serious problem that is encountered in conjunction with detecting various types of liquid that can collect on a surface is that the surface may not comprise a smooth metal, plastic, or concrete, but rather might be a textile floor covering, as is found not only in private rooms but also very often in commercial spaces. This problem is manifested, for example, where there is merely a defect in the water heating system or in water pipes, so that in contrast to a smooth floor or other surface, generally initially only a small area of the textile floor covering becomes soaked, and often this spot is covered by furniture or other devices and hence is not noticed. Thus, water or some other liquid can leak out unnoticed for a long period of time, resulting in serious damage. In addition, the structure of the textile floor covering, for example carpet pile secured to a base, can absorb considerable quantities of liquid and can prevent the same from flowing off, even if the floor or surface has a slight incline.
It is therefore an object of the present invention to provide an apparatus of the aforementioned general type that is suitable for detecting, with great precision, a large number of different liquids, that in addition is in a position to detect various types of liquid that accumulate not only on an unstructured, smooth surface, but also on structured surfaces and even on textile floor coverings, that is very straightforward in construction and requires no skilled artisan for assembly and installation, that is very easy and economical to produce and hence can be employed in large quantities, and that contributes to increasing the general safety.